This Article Full Text Full Text (PDF) Other Versions of this Article: JVI.01940-06v1 81/5/2328    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Jain, S. Articles by Morrison, T. G. Search for Related Content PubMed PubMed Citation Articles by Jain, S. Articles by Morrison, T. G.

 Previous Article  |  Next Article 

Journal of Virology, March 2007, p. 2328-2339, Vol. 81, No. 5
0022-538X/07/$08.00+0     doi:10.1128/JVI.01940-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Thiol/Disulfide Exchange Is Required for Membrane Fusion Directed by the Newcastle Disease Virus Fusion Protein

Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, Massachusetts 01655

Received 6 September 2006/ Accepted 29 November 2006

Newcastle disease virus (NDV), an avian paramyxovirus, initiates infection with attachment of the viral hemagglutinin-neuraminidase (HN) protein to sialic acid-containing receptors, followed by fusion of viral and cell membranes, which is mediated by the fusion (F) protein. Like all class 1 viral fusion proteins, the paramyxovirus F protein is thought to undergo dramatic conformational changes upon activation. How the F protein accomplishes extensive conformational rearrangements is unclear. Since several viral fusion proteins undergo disulfide bond rearrangement during entry, we asked if similar rearrangements occur in NDV proteins during entry. We found that inhibitors of cell surface thiol/disulfide isomerase activity—5'5-dithio-bis(2-nitrobenzoic acid) (DTNB), bacitracin, and anti-protein disulfide isomerase antibody—inhibited cell-cell fusion and virus entry but had no effect on cell viability, glycoprotein surface expression, or HN protein attachment or neuraminidase activities. These inhibitors altered the conformation of surface-expressed F protein, as detected by conformation-sensitive antibodies. Using biotin maleimide (MPB), a reagent that binds to free thiols, free thiols were detected on surface-expressed F protein, but not HN protein. The inhibitors DTNB and bacitracin blocked the detection of these free thiols. Furthermore, MPB binding inhibited cell-cell fusion. Taken together, our results suggest that one or several disulfide bonds in cell surface F protein are reduced by the protein disulfide isomerase family of isomerases and that F protein exists as a mixture of oxidized and reduced forms. In the presence of HN protein, only the reduced form may proceed to refold into additional intermediates, leading to the fusion of membranes.

Published ahead of print on 6 December 2006.

This article has been cited by other articles:

• Meckes, D. G. Jr., Wills, J. W. (2007). Dynamic Interactions of the UL16 Tegument Protein with the Capsid of Herpes Simplex Virus. J. Virol. 81: 13028-13036 [Abstract] [Full Text]